Recanalization Strategy for Chronic Total Occlusions with Tapered and Stiff-Tip Guidewire

The Results of CTO New techniQUE for STandard Procedure (CONQUEST) Trial

ABSTRACT: Background. The success rate of percutaneous coronary intervention (PCI) for chronic total coronary occlusion (CTO) lesions varies depending on the guidewire manipulation skills of the operator. The standardization of guidewire technique is very important. A new technique with a new tapered wire (Conquest, Confianza Pro™) was tested to verify effectiveness for higher initial success rates and standardization of PCI for CTO. Methods. A prospective, multicenter registry was conducted at 6 investigational sites. In the CONQUEST trial, The CTO lesions were treated by using an intermediate guidewire to cross the lesion. If it did not cross, the guidewire was changed to the Conquest guidewire. If it did not cross, “seesaw-wiring” or the “parallel-wire technique” was performed. The primary endpoint was the initial procedural success rate. Results. A total of 110 patients representing 116 CTO lesions were treated from July 2003 through March 2004. The procedural success rate was 86.2% on the first try, and 88.8% on the second try, respectively. The guidewire success rate on the second try was 90.5% during the hospital stay; no deaths, or acute myocardial infarctions were confirmed. Two patients deteriorated into tamponade, and surgical or percutaneous drainage was performed in each patient without any sequelae. Conclusions. A guidewire technique in PCI for CTOs that starts with the intermediate guidewire and moves to the Confianza Pro tapered guidewire, either alone or by performing a see-saw or parallel-wire technique, can achieve a high initial success rate with an acceptably low major complication rate. J INVASIVE CARDIOL 2008;20:571–577 Chronic total occlusion (CTO) lesions are encountered in approximately 30% of all percutaneous coronary intervention (PCI) cases,1 and while nearly one-third of those CTO lesions are treated percutaneously, many more are treated with coronary artery bypass graft surgery (CABG) because of the low success and high restenosis rates,2–5 resulting in a limited utilization of PCI in the treatment of CTO lesions. In addition, PCI for CTOs often had a higher-than-normal rate of complications, and the inherent longer time of radiation exposure, as well as the need for a greater amount of contrast media, deterred cardiologists from aggressively treating these lesions. The advent of drug-eluting stents (DES) has resulted in an in-stent restenosis rate of Methods Definition of CTOs and inclusion criteria. CTO was defined as an occlusion with an estimated age of > 30 days along with a thrombolysis in myocardial infarction (TIMI) 0 flow confirmed by coronary angiography. The success rate was examined in subgroups by using another CTO definition in which occlusion age was > 3 months. Registration was limited to patients > 20 years of age who were undergoing an initial attempt or a first planned re-try of CTO recanalization. Guidewire strategy. As in conventional techniques, the guidewire was still introduced with an over-the-wire (OTW) catheter. However, in the new procedure, the first guidewire used was an intermediate-type with a tip stiffness of Registration. Between June 2003 and March 2004, a total of 118 cases were registered electronically through the Internet by 6 centers in Japan. Cases were required to be registered prior to the procedure initiation, and once registered, were prohibited from deletion. Core laboratory. Itabashi Central General Hospital was assigned as the core laboratory for coronary angiographic evaluation for both quantitative coronary angiography (QCA) and qualitative coronary angiography. The latter included the morphology of the occlusion (abrupt or tapered), tortuosity, degree of calcification, presence of a side branch within 3 mm of the occlusion, presence of bridging collaterals, Rentrop classification of collateral circulation and ruling out of functional total occlusions. Endpoints. The primary endpoint is the initial procedural success rate with secondary endpoints as follows: a) cumulative final procedural success rate including the registered re-try cases; b) guidewire manipulation steps; c) guidewire success rate; d) guidewire manipulation time; e) total volume of contrast medium use; f) X-ray exposure time; and g) complications. Data were expressed as mean ± standard deviation (SD) for continuous variables and as numbers with percentage for categorical variables. The underlying factors were normalized to patient count and lesion factors to lesion count. Setting number of cases. Accepting the null hypothesis if an initial success rate of 80% was not achieved, an initial target number of 120 cases was proposed. This would allow for 108 necessary cases and 10 dropout cases in accordance with the significance level of 0.05 in a two-sided test and the detection power of 80%, which should also be valid in assessing for the initial success rate of 90% that was set as the opposition hypothesis. Results Characteristics of patients and lesions. Out of 118 registered cases, 8 were excluded from the registry because their occlusions were judged to be functional by the core lab. The mean age was 66.3 ± 10.6 years; the great majority was male; 37% had history of previous myocardial infarction and 9% had prior CABG. Coronary risk factors were present in 35–56% of patients. Three cases (2.7%) were on chronic hemodialysis (Table 1). Single-vessel coronary disease (1VD; 51.8% of patients) and double-vessel disease (2VD in 30.9% of patients) made for 82% of the patients, and the remaining had triple-vessel disease (3VD). CTO lesions involved the left anterior descending artery (LAD) more frequently, followed by the right coronary artery (RCA), and lastly, the left circumflex artery (LCX). The occlusion age could be estimated in only one-quarter of the patients, and was unknown in the remaining (Table 2). Bilateral coronary angiography was performed in 80% of cases, and biplane cine angiography equipment was used in 53% of cases. Success rate and guidewire strategy. The success rate of the first step (intermediate guidewire) was 14.6% (17/116), second step (Conquest series guidewire) 46.9% (46/98), and third step (see-saw wiring) 78% (39/50), resulting in an initial guidewire success rate of 87.9% (102/116), and including the 3 registered first re-try procedures, a cumulative success rate of 90.5% (105/116). Procedural success was achieved in 86.2% and 88.8% respectively which proved to be significantly higher (p Quantitative and qualitative evaluation of coronary angiography and success rate. By QCA analysis, the mean lesion (occlusion) length was 17.6 ± 15.6 mm (Table 4). Importantly, the various lesion characteristics that were thought to potentially influence the success rates made no differences except for bridging collaterals. Procedures were successful in all 5 cases, with marked tortuous lesions of > 45º angulations. The success rates for lesions > 20 mm and Complications. No patient died, had acute myocardial infarction or required emergency CABG, but 2 patients developed cardiac tamponade several hours post procedure, necessitating catheter or surgical drainage, without any sequelae. Although guidewire perforation was confirmed in 9 cases (7.8%), obvious extravasation could not be demonstrated. Dissection was found in 1 case and slow-flow in 2 cases (Table 5). Discussion Comparison with previous data. The success rate of PCI for CTOs is still unsatisfactory. Although a single-center observational study showed a high success rate of 81% in 1995,19 in general, the success rate for recanalizing CTO lesions was around 70%. In that report, it was also stated that not all operators could anticipate the optimal results. The inability to cross the lesion with a guidewire is the reason for failure in more than 75% of unsuccessful attempts;20 therefore, new guidewire systems to facilitate crossing of CTO lesions have been developed. Michalis et al used vibrational angioplasty and reported a success rate of 86.1%.21 It was the best result achieved using conventional soft guidewires with an additional simple mechanical microvibration device, which seemed to work well for relatively soft and short CTO lesions. Recently, Gloria reported a similar novel vibration angioplasty Crosser system, for which the technical success rate was 69% in lesions in which there was an initial unsuccessful guidewire attempt. These results are expected to be evaluated in a dedicated study. The Laserwire (Spectranetics, Inc., Colorado Springs, Colorado), a 0.018 inch guidewire capable of carrying an excimer laser beam to facilitate advancement within the occlusion, was examined in two independent multicenter registries from Europe and the United States. In the Europe TOTAL trial, Serruys et al13 reported no additional benefit from using the Laserwire over conventional guidewires in the success rate of guidewire crossing within 30 minutes (52.8% vs 47.2%; p = 0.33) in 303 cases. In the U.S. TOTAL trial, Oesterle et al14 reported an initial success rate of 61% after conventional guidewires had failed to cross the lesion. However, those procedures were complicated by periprocedural acute myocardial infarction in 3.9% of patients, cardiac tamponade in 1.7% and death in 1.1% of the cases, which were unacceptably high. The Safecross is a new guidewire system that uses optical coherence reflectometry to differentiate plaque from vesse wall22 and radiofrequency power to ablate hard tissues in front of the tip advancing through the occluded segment. Although a clinical report15 demonstrated a success rate for guidewire crossing CTOs of 51.7% after conventional guidewires had failed, the relatively poor torque precludes its broad application, especially in tortuous vessels. Guidewires with lubricious hydrophilic coatings (the Crosswire,12 and the Choice PT guidewire23) or slippery hydrophobic Teflon coatings (the Shinobi wire24) have been evaluated in clinical settings; and reasonable success rates were reported, but the improvement is far from being significant when compared with conventional guidewires. Significance of the strategy using Conquest Pro. The configuration of the Conquest Pro guidewire with a proximal 0.014 inch shaft, tapered to a 0.009 inch tip with a 9 g stiffness capped by a ball, maximizes the chances of negotiating through the occlusion by taking advantage of the two working mechanisms common to all wires: penetration and drilling. The Conquest Pro guidewire primarily uses “penetration effects”, which enables advancing the guidewire through the occlusion without the need for vigorous tip rotation, and to lesser extent, “drilling” achieved by rotation of the guidewire tip. Although by virtue of the “penetration” effect of the Conquest guidewire, the guidewire tip may slip into the subintimal space, the size of the created pseudolumen may be smaller because of the thinner guidewire tip and reduced rotation. This may make re-entering the distal true lumen from the subintimal track with the guidewire tip by penetrating the media more likely than when a large pseudolumen space has resulted from using conventional guidewires based mainly on the “drilling” effect of vigorous tip rotation. Furthermore, should the guidewire perforate the vessel, the thin-tapered tip makes a smaller hole, with a lower risk of major extravasation. Saito25 reported that tapered-tip guidewires were more advantageous in treating CTO lesions based on a single-center experience, and our multicenter results confirmed those results. The Conquest Pro guidewire has an effective hydrophilic coating on the spring-coil shaft, but not on the ball tip, which facilitates capture of the small dimple at the entry point leading the guidewire tip into the true lumen while enhancing its manipulation by less friction, thus minimizing chances of entering into the subintimal space. The parallel-wire method makes use of two guidewires simultaneously to approach the distal true lumen of CTO lesions. It is hypothesized that the first guidewire serves as a landmark for the operator while the second guidewire is advanced to negotiate the true lumen. When a parallel-wire method is performed using two full sets of over-the-wire microcatheters with a guidewire inside each, we named it the “see-saw” wiring method, because if the second wire failed to negotiate the distal true lumen, the first wire would now change its role to penetrate the true lumen while utilizing the second wire as a landmark, and their roles could be alternated in a back-and-forth sequence (“see-saw”) at any moment without having to exchange the microcatheter or the guidewire, as is required with the conventional parallel-wire method. Success rate and standardization. To avoid overdoing the initial attempt just to achieve success, a planned first re-try was registered as part of the initial procedure. However the primary guidewire success rate being as high as 88.8%, only 3 cases were re-scheduled for a planned first re-try, thus the resulting cumulative ultimate success rate was 90.5%. The success rate of 90.1%, by using the CTO definition of occlusion age > 3 months, was almost equivalent to the overall success rate. Considering this was a multicenter, prospective registry with strict checks by a core laboratory, we believe it meets the standardization criteria of 90% success rate, a figure far better than the generally aimed 80% utilizing a conventional guidewire.19,25 In all unfavorable lesion characteristics such as abrupt cut-off, bridge collateral, rich collateral flow, side branch at occlusion site, severe calcification, bending occlusion and long lesion, the success rates were higher than 80%, and not significantly different between present and absent of these characteristics except for bridge collateral. These success rates were higher than previously reported results of 30–60%.26 Even for high success rates, the consumption of a relatively high amount of contrast media and long fluoroscopy times are major problems which should be resolved. Although two cases were complicated by cardiac tamponade, no other major complications resulting in death, AMI or urgent CABG were observed. Both cases occurred at the same center and were guidewire failures despite lengthy attempts. Cardiac tamponade due to contrast media leak developed after patients had returned to their wards was not detected while in the catheterization laboratory. Both patients recovered promptly without any sequelae following surgical or percutaneous drainage. It should be emphasized that the risk of extravasation may increase if the guidewire punches out repeatedly, regardless of the wire type, even if the hole is small at the perforation site, as with the Conquest Pro. To avoid such risks, it is best to re-try if a suspicion of perforation is entertained rather than perservering for success. Thus it is concluded that this new “seesaw” penetrating strategy using the Conquest (Confianza) Pro guidewire could become the standard strategy of PCI for CTO. The most significant finding of this trial may be the fact that there were no significant differences between the success rates among CTO cases with different morphology or occlusion duration, except for presence of bridging collaterals. Historical comparison. Although we cannot compare the result of this new strategy with older strategies directly, there are historical data from the most experienced hospital of this study group. The success rate in the era before the Conquest guidewire was 69.3% of 277 CTO lesions, and in the era of the Conquest guidewire without the see-saw wire technique was 81.5% of 216 lesions (Figure 7). The success rate of this trial is significantly higher than these historical results (p = 0.03 and p Limitations. This CONQUEST trial is a prospective, multicenter6 registry rather than a randomized, controlled trial involving only a very limited number of operators who were accustomed to the use of the Conquest Pro guidewire and a small number of lesions116 that merely met the minimal criterion with a statistic meaning. In order to confirm the conclusions of this CONQUEST trial, a larger study may be needed with a greater number of centers, patients and lesions. Conclusion A guidewire technique in PCI for CTO starting with the intermediate guidewire and proceeding to the Conquest Pro tapered guidewire, either alone or following the “seesaw” parallel wire technique, can achieve a high initial success rate with an acceptable low major complication rate.

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